为什么磁悬浮列车几乎不受摩擦阻力，能跑得极快？
Why does a maglev train face almost no friction and reach very high speeds?
磁悬浮利用同名磁极相斥或电磁吸力让列车悬空，车身与轨道不接触，消除了滚动和滑动摩擦。只剩空气阻力，因此能达到普通列车难以企及的速度。
Maglev uses repelling or attracting magnetic forces to levitate the train so the body never touches the track, removing rolling and sliding friction. Only air resistance remains, allowing speeds ordinary trains cannot reach.
难度 专业 · 适合 高中(15-18)
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
别莱利曼,《趣味物理学》,多种中译本
Ya. I. Perelman, Physics for Entertainment, various translations
独立核验依据 · Independent verification: 核验依据 2 OPENLIBRARY 标识 /works/OL8643229W：Physics for Entertainme
#磁力 #悬浮 #摩擦物理
为什么用砂纸反复打磨木头或金属会感到发热？
Why does rubbing sandpaper on wood or metal make it feel hot?
摩擦做功把机械能转化为内能，微观上粗糙表面相互刮擦使接触点的分子振动加剧。能量以热的形式积累，所以摸上去发烫。
Friction does work that converts mechanical energy into internal energy; at the microscopic level the rough surfaces scrape and agitate the molecules at contact points. The energy builds up as heat, so the spot feels hot.
难度 进阶 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
别莱利曼,《趣味物理学》,多种中译本
Ya. I. Perelman, Physics for Entertainment, various translations
独立核验依据 · Independent verification: 核验依据 2 OPENLIBRARY 标识 /works/OL8643229W：Physics for Entertainme
#摩擦 #做功 #摩擦物理
为什么鞋底磨平之后在湿地上更容易打滑？
Why do worn-flat shoe soles slip more easily on wet ground?
新鞋底的花纹能排开表面水膜并增加接触咬合，摩擦系数高。磨平后水膜难以排出，橡胶与地面的真实接触面积减小，摩擦下降，容易打滑。
New treads channel away surface water and bite into the ground, giving high friction. Once worn flat, water films cannot be expelled and real contact area drops, lowering friction and making slips likely.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
别莱利曼,《趣味物理学》,多种中译本
Ya. I. Perelman, Physics for Entertainment, various translations
独立核验依据 · Independent verification: 核验依据 2 OPENLIBRARY 标识 /works/OL8643229W：Physics for Entertainme
#摩擦 #磨损 #摩擦物理
为什么汽车轮胎上要刻出许多花纹？
Why do car tires have grooves and patterns?
花纹能在湿滑路面排出轮胎与地面的水膜，保持橡胶直接接触路面，维持摩擦和抓地力。同时花纹也帮助散热和分散磨损，提升安全与寿命。
The grooves channel water away from between the tire and road, keeping the rubber in contact for friction and grip on wet surfaces. They also aid heat dissipation and even out wear, improving safety and lifespan.
难度 入门 · 适合 大众
CC BY 4.0 · 已核验 · Verified 2026-08-23 · 2 条独立证据
来源 · Source
别莱利曼,《趣味物理学》,多种中译本
Ya. I. Perelman, Physics for Entertainment, various translations
独立核验依据 · Independent verification: 核验依据 2 OPENLIBRARY 标识 /works/OL8643229W：Physics for Entertainme
#摩擦 #抓地 #摩擦物理